Structure of the venus middle atmosphere: Venera 15 fourier spectrometry data revisited

Abstract

The data obtained by Infrared Fourier Spectrometer on board Venera 15 Orbiter are revisited. The new database of temperature and aerosol profiles is created for the altitude range 55–100 km. The main improvements concern the involving of the whole spectral range free from absorption by any gases but CO 2 into the temperature retrieval procedure. Besides the CO 2 15 μm fundamental band, this range also includes the weak hot and isotopic CO 2 bands. HITRAN-96 spectral database was used for calculation of the gaseous absorption coefficients. The diurnal variations at the isobaric levels are investigated. At low latitudes at the altitude h > 85 km a minimal temperature is observed in the afternoon, and a maximal one is on the morning day side. The temperature differences reach 20 K near 0.1 mb level. The temperature difference changes its sign below 1 mb level: in the afternoon it is warmer by more than 10 K than in the morning. The density of the clouds at all latitudes is found to be higher in the afternoon than in the morning. In the coldest parts of the ‘cold collar’ the clouds are found to be composed of the mode 3 particles. The thermal zonal wind field reveals the presence of the midlatitude jet, connected with the ‘cold collar’. The low latitude jet near 85 km, connected with the temperature inversion above this level, is observed. It is also possible that another low latitude jet exists near the cloud tops at low latitudes.